Polycrystalline diamond, polycrystalline diamond compacts, methods of making same, and applications

ABSTRACT

Embodiments of the invention relate to polycrystalline diamond compacts (“PDC”) exhibiting enhanced diamond-to-diamond bonding. In an embodiment, a PDC includes a polycrystalline diamond (“PCD”) table bonded to a substrate. At least a portion of the PCD table includes a plurality of diamond grains defining a plurality of interstitial regions. The plurality of interstitial regions includes a metal-solvent catalyst. The plurality of diamond grains exhibit an average grain size of about 30 μm or less. The plurality of diamond grains and the metal-solvent catalyst collectively exhibit an average electrical conductivity of less than about 1200 S/m. Other embodiments are directed to PCD, employing such PCD, methods of forming PCD and PDCs, and various applications for such PCD and PDCs in rotary drill bits, bearing apparatuses, and wire-drawing dies.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.13/486,578 filed on 1 Jun. 2012, which is a continuation-in-part of U.S.patent application Ser. No. 12/858,906 filed on 18 Aug. 2010, which is adivisional of U.S. patent application Ser. No. 12/244,960 filed on 3Oct. 2008 (now U.S. Pat. No. 7,866,418), the contents of each of theforegoing applications are incorporated herein, in their entirety, bythis reference.

BACKGROUND

Wear-resistant, superabrasive compacts are utilized in a variety ofmechanical applications. For example, polycrystalline diamond compacts(“PDCs”) are used in drilling tools (e.g., cutting elements, gagetrimmers, etc.), machining equipment, bearing apparatuses, wire-drawingmachinery, and in other mechanical apparatuses.

PDCs have found particular utility as superabrasive cutting elements inrotary drill bits, such as roller-cone drill bits and fixed-cutter drillbits. A PDC cutting element typically includes a superabrasive diamondlayer commonly referred to as a diamond table. The diamond table may beformed and bonded to a substrate using a high-pressure, high-temperature(“HPHT”) process. The PDC cutting element may also be brazed directlyinto a preformed pocket, socket, or other receptacle formed in the bitbody. The substrate may often be brazed or otherwise joined to anattachment member, such as a cylindrical backing. A rotary drill bittypically includes a number of PDC cutting elements affixed to the bitbody. It is also known that a stud carrying the PDC may be used as a PDCcutting element when mounted to a bit body of a rotary drill bit bypress-fitting, brazing, or otherwise securing the stud into a receptacleformed in the bit body.

Conventional PDCs are normally fabricated by placing a cemented carbidesubstrate into a container with a volume of diamond particles positionedadjacent to the cemented carbide substrate. A number of such cartridgesmay be loaded into an HPHT press. The substrates and volume of diamondparticles are then processed under HPHT conditions in the presence of acatalyst material that causes the diamond particles to bond to oneanother to form a matrix of bonded diamond grains defining apolycrystalline diamond (“PCD”) table that is bonded to the substrate.The catalyst material is often a metal-solvent catalyst (e.g., cobalt,nickel, iron, or alloys thereof) that is used for promoting intergrowthof the diamond particles.

In one conventional approach, a constituent of the cemented carbidesubstrate, such as cobalt from a cobalt-cemented tungsten carbidesubstrate, liquefies and sweeps from a region adjacent to the volume ofdiamond particles into interstitial regions between the diamondparticles during the HPHT process. The cobalt acts as a catalyst topromote intergrowth between the diamond particles, which results information of bonded diamond grains. Often, a solvent catalyst may bemixed with the diamond particles prior to subjecting the diamondparticles and substrate to the HPHT process.

The presence of the solvent catalyst in the PCD table is believed toreduce the thermal stability of the PCD table at elevated temperatures.For example, the difference in thermal expansion coefficient between thediamond grains and the solvent catalyst is believed to lead to chippingor cracking of the PCD table during drilling or cutting operations,which can degrade the mechanical properties of the PCD table or causefailure. Additionally, some of the diamond grains can undergo a chemicalbreakdown or back-conversion to graphite via interaction with thesolvent catalyst. At elevated high temperatures, portions of the diamondgrains may transform to carbon monoxide, carbon dioxide, graphite, orcombinations thereof, thus degrading the mechanical properties of thePDC.

One conventional approach for improving the thermal stability of a PDCis to at least partially remove the solvent catalyst from the PCD tableof the PDC by acid leaching. However, removing the solvent catalyst fromthe PCD table can be relatively time consuming for high-volumemanufacturing. Additionally, depleting the solvent catalyst may decreasethe mechanical strength of the PCD table.

Despite the availability of a number of different PCD materials,manufacturers and users of PCD materials continue to seek PCD materialsthat exhibit improved mechanical and/or thermal properties.

SUMMARY

Embodiments of the invention relate to PCD exhibiting enhanceddiamond-to-diamond bonding and related PDCs, rotary drill bits, andmethods of fabrication. In an embodiment, PCD includes a plurality ofdiamond grains defining a plurality of interstitial regions. Theplurality of diamond grains exhibit an average grain size of about 30 μmor less. A metal-solvent catalyst occupies at least a portion of theplurality of interstitial regions. The plurality of diamond grains andthe metal-solvent catalyst collectively may exhibit an averageelectrical conductivity of less than about 1200 S/m.

In an embodiment, a PDC includes a PCD table having a plurality ofdiamond grains defining a plurality of interstitial regions. The PCDtable is bonded to a substrate. A metal-solvent catalyst occupies atleast a portion of the plurality of interstitial regions. The pluralityof diamond grains exhibit an average grain size of about 30 μm or less.The plurality of diamond grains and the metal-solvent catalystcollectively may exhibit an average electrical conductivity of less thanabout 1200 S/m.

In an embodiment, a method includes enclosing a plurality of diamondparticles and a metal-solvent catalyst in a pressure transmitting mediumto form a cell assembly. The plurality of the diamond particles exhibitsan average particle size of about 30 μm or less. The method furtherincludes subjecting the cell assembly to a temperature of at least about1000° Celsius and a pressure in the pressure transmitting medium of atleast about 7.5 GPa to form PCD. The PCD exhibits an average electricalconductivity of less than about 1200 S/m.

In an embodiment a rotary drill bit includes a bit body including aleading end structure configured to facilitate drilling a subterraneanformation. The rotary drill bit also includes a plurality of cuttingelements mounted to the blades. At least one of the plurality of cuttingelements includes a PCD element. At least a portion of the PCD elementincludes a plurality of diamond grains defining a plurality ofinterstitial regions, the plurality of interstitial regions, includingmetal-solvent catalyst. The at least a portion of the PCD elementexhibits an average electrical conductivity of less than about 1200 S/m.

Further embodiments relate to applications utilizing the disclosed PCDand PDCs in various articles and apparatuses, such as rotary drill bits,bearing apparatuses, wire-drawing dies, machining equipment, and otherarticles and apparatuses.

Features from any of the disclosed embodiments may be used incombination with one another, without limitation. In addition, otherfeatures and advantages of the present disclosure will become apparentto those of ordinary skill in the art through consideration of thefollowing detailed description and the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings illustrate several embodiments of the invention, whereinidentical reference numerals refer to identical elements or features indifferent views or embodiments shown in the drawings.

FIG. 1A is a schematic diagram of an example of a magnetic saturationapparatus configured to magnetize a PCD sample approximately tosaturation.

FIG. 1B is a schematic diagram of an example of a magnetic saturationmeasurement apparatus configured to measure a saturation magnetizationof a PCD sample.

FIG. 2 is a schematic diagram of an example of a coercivity measurementapparatus configured to determine a coercivity of a PCD sample.

FIG. 3A is an isometric view of an embodiment of a PDC including a PCDtable formed from any of the PCD embodiments disclosed herein.

FIG. 3B is a functional block diagram of an embodiment of a multi-proberesistance measurement testing system configured to measure electricalresistance of a PCD table that may be used to measure electricalconductivity of the PCD or PCD tables disclosed herein.

FIG. 4 is a schematic diagram for four-probe electrical resistancemeasurements on a PDC sample using the system shown in FIG. 3A.

FIG. 5 is a top isometric view of the sensor-probe arrangement of thetesting system shown in FIG. 4.

FIG. 6A is an isometric view of an embodiment of a sample-holderassembly for holding a PDC sample to be tested.

FIG. 6B is a cross-sectional view of the sample-holder assembly shown inFIG. 6A, with a PDC sample to be tested held therein.

FIGS. 7A and 7B are electrical conductivity distributions in PCD tablesof two different PDC cutter samples, with the electrical conductivitygrey scale in Siemens/meter (“S/m”).

FIG. 8A is a cross-sectional view of an embodiment of a PDC including aPCD table formed from any of the PCD embodiments disclosed herein.

FIG. 8B is a cross-sectional view of an embodiment of a PDC illustratinga PCD table that has been leached to deplete metal-solvent catalyst froma region thereof.

FIG. 8C is an enlarged cross-sectional view of FIG. 8A of the PDC shownin FIG. 8A.

FIG. 8D is an electrical conductivity gradient profile of the PCD tableshown in FIG. 8A showing the magnitude of the electrical conductivityrepresented as arrow length, with the magnitude of the electricalconductivity decreasing with distance from the working surface.

FIG. 9 is a graph illustrating the electrical conductivity, σ, versuscell pressure relationship in which electrical conductivity decreaseswith increasing cell pressure.

FIG. 10 is a graph illustrating the wear volume from a vertical turretlathe (“VTL”) test versus cell pressure relationship in which wearvolume decreases with increasing cell pressure.

FIG. 11A is a schematic illustration of a method of fabricating the PDCshown in FIG. 8A.

FIG. 11B is a schematic illustration of a method of fabricating anotherembodiment of a PDC using the methods disclosed herein.

FIG. 12 is a graph illustrating residual principal stress versussubstrate thickness that was measured in a PCD table of a PDC fabricatedat a pressure above about 7.5 GPa and a PCD table of a conventionallyformed PDC.

FIG. 13 is an isometric view of an embodiment of a rotary drill bit thatmay employ one or more of the disclosed PDC embodiments.

FIG. 14 is a top elevation view of the rotary drill bit shown in FIG.13.

FIG. 15 is an isometric cut-away view of an embodiment of athrust-bearing apparatus that may utilize one or more of the disclosedPDC embodiments.

FIG. 16 is an isometric cut-away view of an embodiment of a radialbearing apparatus that may utilize one or more of the disclosed PDCembodiments.

FIG. 17 is a schematic isometric cut-away view of an embodiment of asubterranean drilling system including the thrust-bearing apparatusshown in FIG. 15.

FIG. 18 is a side cross-sectional view of an embodiment of awire-drawing die that employs a PDC fabricated in accordance with theprinciples described herein.

DETAILED DESCRIPTION

Embodiments of the invention relate to PCD exhibiting enhanceddiamond-to-diamond bonding and related PDCs, rotary drill bits, andmethods of fabrication. It is currently believed by the inventors thatas the sintering cell pressure employed during the HPHT process used tofabricate such PCD is moved further into the diamond-stable region awayfrom the graphite-diamond equilibrium line, the rate of nucleation andgrowth of diamond increases. Such increased nucleation and growth ofdiamond between diamond particles (for a given diamond particleformulation) may result in PCD being formed exhibiting a relativelylower metal-solvent catalyst content with an associated relatively lowaverage electrical conductivity, a higher coercivity, a lower specificmagnetic saturation, and/or a lower specific permeability (i.e., theratio of specific magnetic saturation to coercivity) than PCD formed ata lower sintering pressure. Embodiments also relate to PDCs having a PCDtable comprising such PCD, methods of fabricating such PCD and PDCs, andapplications for such PCD and PDCs in rotary drill bits, bearingapparatuses, wire-drawing dies, machining equipment, and other articlesand apparatuses.

PCD Embodiments

According to various embodiments, unleached PCD sintered at a pressureof at least about 7.5 GPa may exhibit a coercivity of 115 Oe or more, ahigh-degree of diamond-to-diamond bonding, a specific magneticsaturation of about 15 G·cm³/g or less, a metal-solvent catalyst contentof about 7.5 weight % (“wt %”) or less, an electrical conductivity ofless than about 1200 S/m, or combinations thereof. The PCD includes aplurality of diamond grains directly bonded together viadiamond-to-diamond bonding to define a plurality of interstitialregions. At least a portion of the interstitial regions or, in someembodiments, substantially all, or a substantial portion of theinterstitial regions may be occupied by a metal-solvent catalyst, suchas iron, nickel, cobalt, or alloys of any of the foregoing metals. Forexample, the metal-solvent catalyst may be a cobalt-based materialincluding at least 50 wt % cobalt, such as a cobalt alloy.

The diamond grains may exhibit an average grain size of about 50 μm orless, such as about 30 μm or less or about 20 μm or less. For example,the average grain size of the diamond grains may be about 10 μm to about20 μm, about 15 μm to about 19.5 μm, about 15 μm to about 18 μm, about10 μm to about 18 μm, or about 5 μm to about 18 μm. In some embodiments,the average grain size of the diamond grains may be about 10 μm or less,such as about 2 μm to about 5 μm or submicron. The diamond grain sizedistribution of the diamond grains may exhibit a single mode, or may bea bimodal or greater grain size distribution.

The metal-solvent catalyst that occupies the interstitial regions may bepresent in the PCD in an amount of about 7.5 wt % or less. In someembodiments, the metal-solvent catalyst may be present in the PCD in anamount of greater than 0 wt % to about 7.5 wt %, about 3 wt % to about7.5 wt %, greater than 0 wt % to about 6 wt %, or about 3 wt % to about6 wt %. In other embodiments, the metal-solvent catalyst content may bepresent in the PCD in an amount less than about 3 wt %, such as about 1wt % to about 3 wt % or a residual amount to about 1 wt %. Bymaintaining the metal-solvent catalyst content below about 7.5 wt %, thePCD may exhibit a desirable level of thermal stability suitable forsubterranean drilling applications.

Many physical characteristics of the PCD may be determined by measuringcertain magnetic and electrical properties of the PCD because themetal-solvent catalyst may be ferromagnetic. The amount of themetal-solvent catalyst present in the PCD may be correlated with themeasured specific magnetic saturation of the PCD. A relatively largerspecific magnetic saturation indicates relatively more metal-solventcatalyst in the PCD.

The mean free path between neighboring diamond grains of the PCD may becorrelated with the measured coercivity of the PCD. A relatively largecoercivity indicates a relatively smaller mean free path. The mean freepath is representative of the average distance between neighboringdiamond grains of the PCD, and thus may be indicative of the extent ofdiamond-to-diamond bonding in the PCD. A relatively smaller mean freepath, in well-sintered PCD, may indicate relatively morediamond-to-diamond bonding.

As merely one example, ASTM B886-03 (2008) provides a suitable standardfor measuring the specific magnetic saturation and ASTM B887-03 (2008)e1 provides a suitable standard for measuring the coercivity of the PCD.Although both ASTM B886-03 (2008) and ASTM B887-03 (2008) e1 aredirected to standards for measuring magnetic properties of cementedcarbide materials, either standard may be used to determine the magneticproperties of PCD. A KOERZIMAT CS 1.096 instrument (commerciallyavailable from Foerster Instruments of Pittsburgh, Pa.) is one suitableinstrument that may be used to measure the specific magnetic saturationand the coercivity of the PCD.

Generally, as the sintering pressure that is used to form the PCDincreases, the coercivity may increase while the magnetic saturation andelectrical conductivity may decrease. The PCD defined collectively bythe bonded diamond grains and the metal-solvent catalyst may exhibit oneor more of the following properties: a coercivity of about 115 Oe ormore, a metal-solvent catalyst content of less than about 7.5 wt % asindicated by a specific magnetic saturation of about 15 G·cm³/g or less,or an electrical conductivity less than about 1200 S/m. For example, theelectrical conductivity may be an average electrical conductivity of thePCD (e.g., a PCD table) or a region of the PCD. In a more detailedembodiment, the coercivity of the PCD may be about 115 Oe to about 250Oe, the specific magnetic saturation of the PCD may be greater than 0G·cm³/g to about 15 G·cm³/g, and the electrical conductivity may beabout 25 S/m to about 1000 S/m. In an even more detailed embodiment, thecoercivity of the PCD may be about 115 Oe to about 175 Oe, the specificmagnetic saturation of the PCD may be about 5 G·cm³/g to about 15G·cm³/g, and the electrical conductivity may be less than about 750 S/m.In another more detailed embodiment, the coercivity of the PCD may beabout 155 Oe to about 175 Oe, the specific magnetic saturation of thePCD may be about 10 G·cm³/g to about 15 G·cm³/g, and the electricalconductivity may be less than about 500 S/m. In yet a another embodimentthe coercivity of the PCD may be 155 Oe to about 175 Oe, the specificmagnetic saturation of the PCD may be about 10 G·cm³/g to about 15G·cm³/g, and the electrical conductivity may be about 100 S/m to about500 S/m. In another embodiment, the coercivity of the PCD may be about130 Oe to about 160 Oe, the specific magnetic saturation of the PCD maybe about 5 G·cm³/g to about 15 G·cm³/g, and the electrical conductivitymay be about 50 S/m to about 150 S/m. The specific permeability (i.e.,the ratio of specific magnetic saturation to coercivity) of the PCD maybe about 0.10 or less, such as about 0.060 to about 0.090. Despite theaverage grain size of the bonded diamond grains being less than about 30μm, the metal-solvent catalyst content in the PCD may be less than about7.5 wt % resulting in a desirable thermal stability.

As discussed above, the electrical conductivity of the PCD may be lessthan 1200 S/m. In some embodiments, the electrical conductivity may beless than 1000 S/m, such as about 25 S/m to about 1000 S/m. In otherembodiments, the electrical conductivity may be less than 750 S/m. Inanother embodiment, the electrical conductivity may be less than 500S/m, such as about 100 S/m to about 500 S/m. In a more restrictiveembodiment, the electrical conductivity may be about 50 S/m to about 150S/m.

In an embodiment, diamond particles having an average particle size ofabout 18 μm to about 20 μm are positioned adjacent to a cobalt-cementedtungsten carbide substrate and subjected to an HPHT process at atemperature of about 1390° C. to about 1430° C. and a pressure of about7.8 GPa to about 8.5 GPa. The PCD so-formed as a PCD table bonded to thesubstrate may exhibit one or more of the following properties: acoercivity of about 155 Oe to about 175 Oe, a specific magneticsaturation of about 10 G·cm³/g to about 15 G·cm³/g, and a cobalt contentof about 5 wt % to about 7.5 wt %, or an electrical conductivity lessthan about 750 S/m.

In one or more embodiments, a specific magnetic saturation constant forthe metal-solvent catalyst in the PCD may be about 185 G·cm³/g to about215 G·cm³/g. For example, the specific magnetic saturation constant forthe metal-solvent catalyst in the PCD may be about 195 G·cm³/g to about205 G·cm³/g. It is noted that the specific magnetic saturation constantfor the metal-solvent catalyst in the PCD may be composition dependent.

Generally, as the sintering pressure is increased above 7.5 GPa, a wearresistance of the PCD so-formed may increase relative to PCD formed atlower pressures. For example, the G_(ratio) may be at least about4.0×10⁶, such as about 5.0×10⁶ to about 15.0×10⁶ or, more particularly,about 8.0×10⁶ to about 15.0×10⁶. In some embodiments, the G_(ratio) maybe at least about 30.0×10⁶. The G_(ratio) is the ratio of the volume ofworkpiece cut to the volume of PCD worn away during a cutting process,such as in a vertical turret lathe (“VTL”) test in which the workpieceis cooled during the cutting process. An example of suitable parametersthat may be used to determine a G_(ratio) of the PCD are a depth of cutfor the PCD cutting element of about 0.254 mm, a back rake angle for thePCD cutting element of about 20 degrees, an in-feed for the PCD cuttingelement of about 6.35 mm/rev, a rotary speed of the workpiece to be cutof about 101 rpm, and the workpiece may be made from Barre granitehaving a 914 mm outer diameter and a 254 mm inner diameter. During theG_(ratio) test, the workpiece is cooled with a coolant, such as water.

In addition to the aforementioned G_(ratio), despite the presence of themetal-solvent catalyst in the PCD, the PCD may exhibit a thermalstability that is close to, substantially the same as, or greater than apartially leached PCD material formed by sintering a substantiallysimilar diamond particle formulation at a lower sintering pressure(e.g., up to about 5.5 GPa) and in which the metal-solvent catalyst(e.g., cobalt) is leached therefrom to a depth of about 60 μm to about100 μm from a working surface. The thermal stability of the PCD may beevaluated by measuring the distance cut in a workpiece prior tocatastrophic failure, without using coolant, in a vertical lathe test(e.g., vertical turret lathe or a vertical boring mill). An example ofsuitable parameters that may be used to determine thermal stability ofthe PCD are a depth of cut for the PCD cutting element of about 1.27 mm,a back rake angle for the PCD cutting element of about 20 degrees, anin-feed for the PCD cutting element of about 1.524 mm/rev, a cuttingspeed of the workpiece to be cut of about 1.78 m/sec, and the workpiecemay be made from Barre granite having a 914 mm outer diameter and a 254mm inner diameter. In an embodiment, the distance cut in a workpieceprior to catastrophic failure as measured in the above-describedvertical lathe test may be at least about 1300 m, such as about 1300 mto about 3950 m.

PCD formed by sintering diamond particles having the same diamondparticle size distribution as a PCD embodiment of the invention, butsintered at a pressure of, for example, up to about 5.5 GPa and attemperatures in which diamond is stable may exhibit a coercivity ofabout 100 Oe or less, a specific magnetic saturation of about 16 G·cm³/gor more, and an electrical conductivity of about 750 S/m or more. Thus,in one or more embodiments of the invention, PCD exhibits ametal-solvent catalyst content of less than 7.5 wt % and a greateramount of diamond-to-diamond bonding between diamond grains than that ofa PCD sintered at a lower pressure, but with the same precursor diamondparticle size distribution and catalyst.

It is currently believed by the inventors that forming the PCD bysintering diamond particles at a pressure of at least about 7.5 GPa maypromote nucleation and growth of diamond between the diamond particlesbeing sintered so that the volume of the interstitial regions of the PCDso-formed is decreased compared to the volume of interstitial regions ifthe same diamond particle distribution was sintered at a pressure of,for example, up to about 5.5 GPa and at temperatures where diamond isstable. For example, the diamond may nucleate and grow from carbonprovided by dissolved carbon in metal-solvent catalyst (e.g., liquefiedcobalt) infiltrating into the diamond particles being sintered,partially graphitized diamond particles, carbon from a substrate, carbonfrom another source (e.g., graphite particles and/or fullerenes mixedwith the diamond particles), or combinations of the foregoing. Thisnucleation and growth of diamond in combination with the sinteringpressure of at least about 7.5 GPa may contribute to PCD so-formedhaving a metal-solvent catalyst content of less than about 7.5 wt %.

FIGS. 1A, 1B, and 2 schematically illustrate the manner in which thespecific magnetic saturation and the coercivity of the PCD may bedetermined using an apparatus, such as the KOERZIMAT CS 1.096instrument. FIG. 1A is a schematic diagram of an example of a magneticsaturation apparatus 100 configured to magnetize a PCD sample tosaturation. The magnetic saturation apparatus 100 includes a saturationmagnet 102 of sufficient strength to magnetize a PCD sample 104 at leastapproximately to saturation. The saturation magnet 102 may be apermanent magnet or an electromagnet. In the illustrated embodiment, thesaturation magnet 102 is a permanent magnet that defines an air gap 106,and the PCD sample 104 may be positioned on a sample holder 108 withinthe air gap 106. When the PCD sample 104 is light-weight, it may besecured to the sample holder 108 using, for example, double-sided tapeor other adhesive so that the PCD sample 104 does not move responsive tothe magnetic field from the saturation magnet 102 and the PCD sample 104is magnetized approximately to saturation.

Referring to the schematic diagram of FIG. 1B, after magnetizing the PCDsample 104 approximately to saturation using the magnetic saturationapparatus 100, a magnetic saturation of the PCD sample 104 may bemeasured using a magnetic saturation measurement apparatus 120. Themagnetic saturation measurement apparatus 120 includes a Helmholtzmeasuring coil 122 defining a passageway dimensioned so that themagnetized PCD sample 104 may be positioned therein on a sample holder124. Once positioned in the passageway, the sample holder 124 supportingthe magnetized PCD sample 104 may be moved axially along an axisdirection 126 to induce a current in the Helmholtz measuring coil 122.Measurement electronics 128 are coupled to the Helmholtz measuring coil122 and configured to calculate the magnetic saturation based upon themeasured current passing through the Helmholtz measuring coil 122. Themeasurement electronics 128 may also be configured to calculate a weightpercentage of magnetic material in the PCD sample 104 when thecomposition and magnetic characteristics of the metal-solvent catalystin the PCD sample 104 are known, such as with iron, nickel, cobalt, andalloys thereof. Specific magnetic saturation may be calculated basedupon the calculated magnetic saturation and the measured weight of thePCD sample 104.

The amount of metal-solvent catalyst in the PCD sample 104 may bedetermined using a number of different analytical techniques. Forexample, energy dispersive spectroscopy (e.g., EDAX), wavelengthdispersive x-ray spectroscopy (e.g., WDX), and/or Rutherfordbackscattering spectroscopy may be employed to determine the amount ofmetal-solvent catalyst in the PCD sample 104.

If desired, a specific magnetic saturation constant of the metal-solventcatalyst content in the PCD sample 104 may be determined using aniterative approach. A value for the specific magnetic saturationconstant of the metal-solvent catalyst in the PCD sample 104 may beiteratively chosen until a metal-solvent catalyst content calculated bythe analysis software of the KOERZIMAT CS 1.096 instrument using thechosen value substantially matches the metal-solvent catalyst contentdetermined via an analytical technique, such as energy dispersivespectroscopy, wavelength dispersive x-ray spectroscopy, and/orRutherford backscattering spectroscopy.

FIG. 2 is a schematic diagram of a coercivity measurement apparatus 200configured to determine a coercivity of a PCD sample. The coercivitymeasurement apparatus 200 includes a coil 202 and measurementelectronics 204 coupled to the coil 202. The measurement electronics 204are configured to pass a current through the coil 202 so that a magneticfield is generated. A sample holder 206 having a PCD sample 208 thereonmay be positioned within the coil 202. A magnetization sensor 210configured to measure a magnetization of the PCD sample 208 may becoupled to the measurement electronics 204 and positioned in proximityto the PCD sample 208.

During testing, the magnetic field generated by the coil 202 magnetizesthe PCD sample 208 approximately to saturation. Then, the measurementelectronics 204 apply a current so that the magnetic field generated bythe coil 202 is increasingly reversed. The magnetization sensor 210measures a magnetization of the PCD sample 208 resulting fromapplication of the reversed magnetic field to the PCD sample 208. Themeasurement electronics 204 determine the coercivity of the PCD sample208, which is a measurement of the reverse magnetic field at which themagnetization of the PCD sample 208 is zero.

Although diamond is not electrically conductive by itself, the sinteringprocess for fabricating PCD introduces small amounts of metal-solventcatalyst (e.g., iron, nickel, cobalt, or alloys thereof) into theinterstitial regions between the bonded diamond grains of the PCD. Forexample, cobalt present during sintering of diamond particles, may actas a metal-solvent catalyst that promotes diamond-to-diamond crystalbonding between the diamond grains during the HPHT sintering process.The macroscopic electrical conductivity of PCD may be related to themetal-solvent catalyst content therein.

Additives to the PCD table may also influence the electricalconductivity thereof. For example, the PCD table may include silicon,silicon carbide, graphite, tungsten, tungsten carbide, boron,combinations thereof, or other selected constituents. Some additives maybe alloyed with the metal-solvent catalyst of the PCD table (prior to orduring the HPHT process) that is present interstitially between bondeddiamond grains. For example, cobalt may be alloyed with tungsten and/orboron.

An embodiment of a PDC 300 including a PCD table 302 and a cementedcarbide substrate 304 is shown in FIG. 3A. The PCD table 302 includes atleast one lateral surface 305, an upper exterior working surface 303,and may include an optional chamfer 307 formed therebetween. It is notedthat at least a portion of the at least one lateral surface 305 and/orthe chamfer 307 may also function as a working surface (e.g., thatcontacts a subterranean formation during drilling operations).

An average electrical conductivity for the PCD table 302 may becalculated based at least partially on at least one measured electricalresistance. Because measurements may be taken at a plurality oflocations, any non-uniformity within the distribution of the electricalconductivity of the PCD table 302 may also be determined, if desired.The existence of such non-uniformities (e.g., regions of significantlyhigher or lower conductivity) can be due to poorly sintered diamondgrains, high metal-solvent catalyst content regions, porosity, and/orcracks.

It will be readily apparent to one of skill in the art that actualcalculation of the electrical conductivity of the PCD table 302 may notbe necessary in every case, as one may alternatively compare themeasured electrical resistance (or another characteristic thatcorrelates to electrical conductivity) to a threshold value known tocorrelate to the threshold electrical conductivity value for a given PCDmicrostructure. In another embodiment, the electrical conductivity maybe measured directly.

FIG. 3B is a functional block diagram of an embodiment of a multi-proberesistance measurement electrical impedance testing (“EIT”) system 400that may be used to measure electrical resistance or impedance. Thesystem 400 includes an EIT unit 401 configured to measure an electricalresistance of the PCD table 302 at a plurality of locations. The EITunit 401 may include a plurality of probes 402 (e.g., 421 spring-loadedprobes) configured to electrically contact a surface 303 of the PCDtable 302 of the PDC 300 (shown in FIG. 4), and a plurality of probes404 (e.g., two probes) to contact the substrate 304 of the PDC sample300. For example, the probes 402 may be spring-loaded pins (e.g., “pogo”pins used in printed circuit board testing) that make contact with thesurface 303 of the PCD table 302. Resistance measurements may beacquired and recorded at a plurality of different locations when 121 ofthe probes 402 and the probes 404 are used in the system 400. Theelectrical resistance measurements may then be reconstructed into a 3Delectrical conductivity distribution of the PCD table 302 using areconstruction algorithm.

The system 400 may be configured to make 4-probe DC resistancemeasurements in the approximate range from 0.1 mΩ to 1Ω on the PDCsample 300. The substrate 304 of the PDC sample 300 may be used as areference conductor. One of the current probes and one of the voltageprobes may be electrically connected to the substrate 304. The 4-probemeasurement setup may be completed by multiplexing one of the topsurface-contacting probes 402 for current injection and another of thetop surface-contacting probes 402 for voltage measurement. Probelocations for the probes 402 are shown in the schematic diagram of FIG.4 as + shapes and only one location is labeled as 402′ for sake ofclarity. Using this probe arrangement, only one large currentmultiplexer and one large voltage multiplexer may be required.

Referring again to FIG. 3B, the system 400 includes a data acquisitionmodule 406 (e.g., a USB data acquisition) coupled to the EIT unit 401.The data acquisition module 406 includes an analog output 408 thatcontrols the output current of a precision current source 410 in therange from about −150 mA to about +150 mA. The current is routed to oneof the 121 sensor probes 402 in contact with the PCD table 302 through a1:128 current multiplexer 412. For example, the current multiplexer 412may be built using commercially available 8:1 analog multiplexers with5Ω maximum series ‘on’ resistance. One of the reference probes 404contacting the substrate 304 serves as a current sink and is grounded. Arespective voltage measurement is taken between the sensor probe 402selected by the 128:1 voltage multiplexer 424 and the second referenceprobe 404 contacting the substrate. The voltage is amplified by aprogrammable-gain instrumentation amplifier 414 and sent to an analoginput 416 of the data acquisition module 406. The amplifier 414 may beprogrammed for gains of, for example, about 1, about 250, about 1000,and about 4000. Unity gain may be used for probe contact resistancemeasurement. A plurality of digital outputs 418 (e.g., 18 total) fromthe data acquisition module 406 control all the multiplexers and theamplifier gain of the amplifier 424.

A computer 420 (e.g., a desktop computer) is coupled to or includes thedata acquisition module 406 therein. The computer 420 receives theelectrical resistance measurements taken by the EIT unit 401 from theanalog input 416 of the data acquisition module 406. The computer 420includes memory 421 storing software thereon containing computerexecutable instructions configured forreconstructing/calculating/analyzing the electrical conductivitydistribution in the PCD table 302 of the PDC sample 300 being tested inaccordance with a reconstruction algorithm and one or more processors423 for executing the computer executable instructions. For example, theone or more processors 423 may control the data acquisition module 406and process the measured resistance data to reconstruct and analyze theelectrical conductivity distribution.

To calibrate the instrument, one or more precision reference resistors422 are provided, such as 50 mΩ, 20 mΩ and 10 mΩ in an embodiment. Asecondary 4:1 voltage multiplexer 425 may be provided to accommodate4-wire measurements of these reference resistors 422. FIG. 3B shows onlyone exemplary reference resistor, but the connections of the otherreference resistors may be similar.

Referring to FIG. 5, an embodiment for a sensor assembly 500 of the EITunit 401 including a plurality of probes 402 is illustrated. In anembodiment, the probes 402 may be arranged in a triangular-grid pattern.It should be noted that other sensor-assembly configurations may beused, e.g., for PDC samples having a different size and/or a differentconfiguration.

FIGS. 6A and 6B illustrate an embodiment of a sample holder 600 thatfacilitates placement of the PDC sample 300 to be tested using thesystem 400 so that reliable electrical contact with the sensor probes402 and 404 may be established. The main body 602 has a cavity 604therein configured for holding the PDC sample 300. The PDC sample 300may be centered and held in place by a resilient member 606 (e.g., asoft O-ring) that is disposed in a groove formed in the main body 602that encircles the PDC sample 300 and defines part of the cavity 604.The resilient member 606 allows turning the part holder upside-down toplace the part on top of the spring-loaded probes 402. The probes 402are installed in and project outwardly from a base 608 havingcorresponding holes (e.g., 121 holes) drilled therein. The sensorassembly 600 may include a cap 610 that carries the reference probes 404that contact the substrate 304 of the PDC sample 300. One or more dowelpins 612 or other alignment structure may extend through sample holdercomponents 602, 608, and 610 to keep them in alignment. Referringspecifically to FIG. 6A, the components of the sample holder 600 may becompressed together so that the probes 402 and 404 are in electricalcontact with the PDC sample 300 by, for example, thumb screws 614 orother compression mechanism.

Optionally, a conductive paste and/or coating (e.g., a conductive greasecontaining silver, copper, gold, or combinations thereof) may be appliedto the surface 303 of the PCD table 302 to help reduce any occurrence ofpoor probe contact.

The described system 400 was used to test a variety of PDC samples. EachPDC sample included a cobalt-cemented carbide substrate having a PCDtable bonded thereto. The PCD tables were comprised of a plurality ofbonded-together diamond grains having cobalt infiltrated from thesubstrate and disposed interstitially between the bonded-togetherdiamond grains. The electrical conductivity distributions of PCD tablesfrom two PDCs having substantially homogenous PCD tables are shown inFIGS. 7A and 7B. Five slices through the 3D electrical conductivitydistribution are shown at varying depths into the PCD table measuredfrom an upper surface of the PCD table (e.g., the upper surface 303 inFIG. 3A). The depth is indicated above each slice. Even though theelectrical conductivity is substantially homogeneous, the averageelectrical conductivity varied from sample to sample, and was found tobe strongly influenced by metal-solvent catalyst content.

Additional details of suitable EIT testing systems and additionalresults are disclosed in U.S. patent application Ser. No. 12/830,878filed on 6 Jul. 2010 and titled METHODS FOR NON-DESTRUCTIVELY TESTING APOLYCRYSTALLINE DIAMOND ELEMENT, RELATED ELECTRICAL IMPEDANCE TOMOGRAPHYSYSTEMS, AND ROTARY DRILL BIT INCLUDING SELECTIVELY ORIENTEDPOLYCRYSTALLINE DIAMOND CUTTER, incorporated herein, in its entirety, bythis reference. It should be noted that the described EIT testing systemis only one suitable system for determining electrical conductivity.Other measurement systems and techniques may be employed.

Embodiments of Methods for Fabricating PCD

As previously discussed, and now discussed in more detail, the PCD maybe formed by sintering a mass of a plurality of diamond particles in thepresence of a metal-solvent catalyst. The diamond particles may exhibitan average particle size of about 50 μm or less, about 10 μm to about 20μm, about 15 μm to about 19.5 μm, about 15 μm to about 18 μm, about 10μm to about 18 μm, or about 5 μm to about 18 μm. In some embodiments,the average particle size of the diamond particles may be about 10 μm orless, such as about 2 μm to about 5 μm or submicron.

In an embodiment, the diamond particles of the mass of diamond particlesmay comprise a relatively larger size and at least one relativelysmaller size. As used herein, the phrases “relatively larger” and“relatively smaller” refer to particle sizes (by any suitable method)that differ by at least a factor of two (e.g., 30 μm and 15 μm).According to various embodiments, the mass of diamond particles mayinclude a portion exhibiting a relatively larger size (e.g., 30 μm, 20μm, 15 μm, 12 μm, 10 μm, 8 μm) and another portion exhibiting at leastone relatively smaller size (e.g., 6 μm, 5 μm, 4 μm, 3 μm, 2 μm, 1 μm,0.5 μm, less than 0.5 μm, 0.1 μm, less than 0.1 μm). In one embodiment,the mass of diamond particles may include a portion exhibiting arelatively larger size between about 10 μm and about 40 μm and anotherportion exhibiting a relatively smaller size between about 1 μm and 4μm. In some embodiments, the mass of diamond particles may comprisethree or more different sizes (e.g., one relatively larger size and twoor more relatively smaller sizes), without limitation.

It is noted that the as-sintered diamond grain size may differ from theaverage particle size of the mass of diamond particles prior tosintering due to a variety of different physical processes, such asgrain growth, diamond particles fracturing, carbon provided from anothercarbon source (e.g., dissolved carbon in the metal-solvent catalyst), orcombinations of the foregoing. The metal-solvent catalyst (e.g., iron,nickel, cobalt, or alloys thereof) may be provided in particulate formmixed with the diamond particles, as a thin foil or plate placedadjacent to the mass of diamond particles, from a cemented carbidesubstrate including a metal-solvent catalyst, or combinations of theforegoing.

In order to efficiently sinter the mass of diamond particles, the massmay be enclosed in a pressure transmitting medium, such as a refractorymetal can, graphite structure, pyrophyllite, and/or other suitablepressure transmitting structure to form a cell assembly. Examples ofsuitable gasket materials and cell structures for use in manufacturingPCD are disclosed in U.S. Pat. No. 6,338,754 and U.S. patent applicationSer. No. 11/545,929, each of which is incorporated herein, in itsentirety, by this reference. Another example of a suitable pressuretransmitting material is pyrophyllite, which is commercially availablefrom Wonderstone Ltd. of South Africa. In an embodiment, the pressuretransmitting material/gasket material may comprise pyrophyllitegenerally in the shape of a cube having a cavity for receiving thecontents to be HPHT processed, with an edge length of the cube beingabout 1.5 inch to about 2.0 inch, about 1.5 inch to about 1.8 inch,about 1.6 inch to about 1.8 inch, or about 1.75 inch to about 1.8 inch(e.g., about 1.775 inch). The cell assembly, including the pressuretransmitting medium and mass of diamond particles therein, is subjectedto an HPHT process using an ultra-high pressure press at a temperatureof at least about 1000° C. (e.g., about 1100° C. to about 2200° C., orabout 1200° C. to about 1450° C.) and a pressure in the pressuretransmitting medium of at least about 7.5 GPa (e.g., about 7.5 GPa toabout 15 GPa) for a time sufficient to sinter the diamond particlestogether in the presence of the metal-solvent catalyst and form the PCDcomprising bonded diamond grains defining interstitial regions occupiedby the metal-solvent catalyst. For example, the pressure in the pressuretransmitting medium employed in the HPHT process may be at least about8.0 GPa, at least about 9.0 GPa, at least about 10.0 GPa, at least about11.0 GPa, at least about 12.0 GPa, or at least about 14 GPa.

The pressure values employed in the HPHT processes disclosed hereinrefer to the pressure in the pressure transmitting medium at roomtemperature (e.g., about 25° C.) with application of pressure using anultra-high pressure press and not the pressure applied to exterior ofthe cell assembly. The actual pressure in the pressure transmittingmedium at sintering temperature may be slightly higher. The ultra-highpressure press may be calibrated at room temperature by embedding atleast one calibration material that changes structure at a knownpressure, such as PbTe, thallium, barium, or bismuth in the pressuretransmitting medium. Further, optionally, a change in resistance may bemeasured across the at least one calibration material due to a phasechange thereof. For example, PbTe exhibits a phase change at roomtemperature at about 6.0 GPa and bismuth exhibits a phase change at roomtemperature at about 7.7 GPa. Examples of suitable pressure calibrationtechniques are disclosed in G. Rousse, S. Klotz, A. M. Saitta, J.Rodriguez-Carvajal, M. I. McMahon, B. Couzinet, and M. Mezouar,“Structure of the Intermediate Phase of PbTe at High Pressure,” PhysicalReview B: Condensed Matter and Materials Physics, 71, 224116 (2005) andD. L. Decker, W. A. Bassett, L. Merrill, H. T. Hall, and J. D. Barnett,“High-Pressure Calibration: A Critical Review,” J. Phys. Chem. Ref.Data, 1, 3 (1972).

In an embodiment, a pressure of at least about 7.5 GPa in the pressuretransmitting medium may be generated by applying pressure to a cubichigh-pressure cell assembly that encloses the mass of diamond particlesto be sintered using anvils, with each anvil applying pressure to adifferent face of the cubic high-pressure assembly. In such anembodiment, a surface area of each anvil face of the anvils may beselectively dimensioned to facilitate application of pressure of atleast about 7.5 GPa to the mass of diamond particles being sintered. Forexample, the surface area of each anvil may be less than about 12.0 cm²(e.g., about 8 cm² to about 10 cm²), or greater than 12.0 cm² such asabout 14.7 cm² to about 17 cm². In an embodiment, a suitable ratio of anedge length of a face of the uncompressed cubic cell assembly containingthe contents prior to being HPHT processed to an edge length of theanvil face may be about 1.20 to about 1.50, such as about 1.3 to about1.4 (e.g., about 1.31, about 1.32, about 1.33, about 1.34, about 1.35,about 1.36, about 1.37, about 1.38, about 1.39, about 1.31 to about1.34), greater than about 1.2, greater than about 1.3, or about 1.4 toabout 1.5. The anvils may be made from a cobalt-cemented tungstencarbide or other material having a sufficient compressive strength tohelp reduce damage thereto through repetitive use in a high-volumecommercial manufacturing environment. Optionally, as an alternative toor in addition to selectively dimensioning the surface area of eachanvil face, two or more internal anvils may be embedded in the cubichigh-pressure cell assembly to further intensify pressure. For example,the article W. Utsumi, N. Toyama, S. Endo and F. E. Fujita, “X-raydiffraction under ultrahigh pressure generated with sintered diamondanvils,” J. Appl. Phys., 60, 2201 (1986) is incorporated herein, in itsentirety, by this reference and discloses that sintered diamond anvilsmay be embedded in a cubic pressure transmitting medium for intensifyingthe pressure applied by an ultra-high pressure press to a workpiece alsoembedded in the cubic pressure transmitting medium.

PDC Embodiments and Methods of Fabricating PDCs

Referring to FIG. 8A, the PCD embodiments may be employed in a PDC forcutting applications, bearing applications, or many other applications.FIG. 8A is a cross-sectional view of the PDC 300 shown in FIG. 3A. ThePCD table 302 may be formed of PCD in accordance with any of the PCDembodiments disclosed herein. The PCD table 302 exhibits at least onelateral dimension “d” (e.g., a diameter), and may include an optionalchamfer 307 formed between a working surface 303 and a lateral surface305.

Although FIG. 8A shows the working surface 303 as substantially planar,the working surface 303 may be concave, convex, or another nonplanargeometry. The substrate 304 may be generally cylindrical or anotherselected configuration, without limitation. Although FIGS. 8A, and 8Cshow an interfacial surface 308 of the substrate 304 as beingsubstantially planar, the interfacial surface 308 may exhibit a selectednonplanar topography, such as a grooved, ridged, or other nonplanarinterfacial surface. The substrate 304 may include, without limitation,cemented carbides, such as tungsten carbide, titanium carbide, chromiumcarbide, niobium carbide, tantalum carbide, vanadium carbide, orcombinations thereof cemented with iron, nickel, cobalt, or alloysthereof. For example, in one embodiment, the substrate 304 comprisescobalt-cemented tungsten carbide.

As illustrated in FIG. 8B, the PCD table 302 shown in FIG. 8A may beacid leached to a selected depth “d” measured from the upper surface 323and/or the chamfer 327 to form a leached region 325 that is depleted ofthe metal-solvent catalyst to form a PDC 320. For example, the leachedregion 325 may generally contour the upper surface 323, the chamfer 327,and the at least one lateral surface 305. The leached region 325 mayextend along a selected length of the at least one lateral surface 305.A residual amount of the metal-solvent catalyst may be present in theleached region 325 even after leaching. For example, the metal-solventcatalyst may comprise about 0.8 weight % to about 1.50 weight % and,more particularly, about 0.9 weight % to about 1.2 weight % of the PCDtable.

The leaching may be performed in a suitable acid (e.g., aqua regia,nitric acid, hydrofluoric acid, or combinations thereof) so that theleached region 325 of the PCD table 302, as shown in FIG. 8B issubstantially free of the metal-solvent catalyst. As a result of themetal-solvent catalyst being depleted from the at least partiallyleached PCD region 325, the PCD table 302 is relatively more thermallystable.

FIG. 8C is an enlarged cross-sectional view of the PCD 300 shown in FIG.8A. FIG. 8C illustrates the thickness “t” of the PCD table 302 thatextends from the working surface 303 to the interfacial surface 308. Inan embodiment, the electrical conductivity of the PCD table 302decreases gradually with distance from the working surface 303 (a regionof relatively higher electrical conductivity) to the interfacial surface308 (a region of relatively lower electrical conductivity), therebycreating an electrical conductivity gradient profile as shown in FIG.8D.

As illustrated in FIG. 8D, the magnitude of the electrical conductivityis represented by the length of arrows 301, with the greatest magnitudeof electrical conductivity at the working surface 303 and the smallestmagnitude of electrical conductivity at the interfacial surface 308.This electrical conductivity gradient profile may exist independently ofthe thickness “t” of the PCD table 302, such as for both thin and thickPCD bodies.

Generally, as the sintering cell pressure that is used to form the PCDincreases, the amount of metal-solvent catalyst in the PCD may decrease.For a given PCD microstructure, the amount of metal-solvent catalystpresent in the PCD may be correlated with the measured electricalconductivity (σ) of the PCD. Accordingly, a relatively small amount ofmetal-solvent catalyst within the PCD generally indicates a relativelysmall value of electrical conductivity.

Electrostatic conductivity measurements may depend on having adequatecontact between pin probes (FIG. 5) and residual metal-solvent catalystin the PCD table. As metal-solvent catalyst content is reduced, it ispossible that pin probes may contact more diamond and less metal-solventcatalyst. As the graph in FIG. 9 illustrates, as sintering cell pressureincreases from approximately 1 GPa to approximately 8 GPa, andmetal-solvent catalyst content decreases, the electrical conductivity ofthe PCD may also decrease in a relatively non-linear fashion. Thesevalues of cell pressure are shown to approach a value of about 8 GPa asvalues for electrical conductivity reach a substantially constant valuewith increasing cell pressure. The inventors believe that the decreasein metal-solvent catalyst content under high pressure may be the reasonfor the non-linearity of conductivity observed at higher cell pressures(e.g., lower cobalt concentrations) as seen in FIG. 9.

As shown in FIG. 10, values for cell pressure and wear volume (theamount of material removed from the PCD table in a VTL test) may besimilarly correlated. FIG. 10 illustrates that as cell pressureincreases from approximately 1 GPa to approximately 8 GPa, the wearvolume is also found to decrease in a relatively non-linear fashion. Asvalues of cell pressure approach a value of approximately 8 GPa, thevalues for wear volume reach a substantially constant value withincreasing cell pressure. The data shown in FIG. 10 may be measuredafter cutting a fixed volume of rock. As the cell pressure increases,the wear resistance may continue to increase until essentially no wearexists after cutting this fixed volume of rock.

FIG. 11A is a schematic illustration of an embodiment of a method forfabricating the PDC 300 shown in FIGS. 3A and 8A. Referring to FIG. 11,a mass of diamond particles 1100 having any of the above-mentionedaverage particle sizes and distributions (e.g., an average particle sizeof about 50 μm or less) is positioned adjacent to the interfacialsurface 308 of the substrate 304. As previously discussed, the substrate304 may include a metal-solvent catalyst. The mass of diamond particles1100 and substrate 304 may be subjected to an HPHT process usingconditions previously described with respect to sintering the PCDembodiments disclosed herein. The PDC 300 so-formed includes the PCDtable 302 that comprises PCD, formed of any of the PCD embodimentsdisclosed herein, integrally formed with the substrate 304 and bonded tothe interfacial surface 308 of the substrate 304. If the substrate 304includes a metal-solvent catalyst, the metal-solvent catalyst mayliquefy and infiltrate the mass of diamond particles 1100 to promotegrowth between adjacent diamond particles of the mass of diamondparticles 1100 to form the PCD table 302 comprised of a body of bondeddiamond grains having the infiltrated metal-solvent catalystinterstitially disposed between bonded diamond grains. For example, ifthe substrate 304 is a cobalt-cemented tungsten carbide substrate,cobalt from the substrate 304 may be liquefied and infiltrate the massof diamond particles 1100 to catalyze formation of the PCD table 302.

Employing selectively dimensioned anvil faces and/or internal anvils inthe ultra-high pressure press used to process the mass of diamondparticles 1100 and substrate 304 enables forming the at least onelateral dimension “d” of the PCD table 302 to be about 0.80 cm or more.Referring again to FIG. 8A, for example, the at least one lateraldimension “d” may be about 0.80 cm to about 3.0 cm and, in someembodiments, about 1.3 cm to about 1.9 cm or about 1.6 cm to about 1.9cm. A representative volume of the PCD table 302 (or any PCD article ofmanufacture disclosed herein) formed using the selectively dimensionedanvil faces and/or internal anvils may be at least about 0.050 cm³. Forexample, the volume may be about 0.25 cm³ to at least about 1.25 cm³ orabout 0.1 cm³ to at least about 0.70 cm³. A representative volume forthe PDC 300 may be about 0.4 cm³ to at least about 4.6 cm³, such asabout 1.1 cm³ to at least about 2.3 cm³.

In other embodiments, a PCD table according to an embodiment may beseparately formed using an HPHT sintering process and, subsequently,bonded to the interfacial surface 308 of the substrate 304 by brazing,using a separate HPHT bonding process, or any other suitable joiningtechnique, without limitation. In yet another embodiment, a substratemay be formed by depositing a binderless carbide (e.g., tungstencarbide) via chemical vapor deposition onto the separately formed PCDtable.

FIG. 11B is a schematic illustration of another embodiment of a methodfor fabricating a PDC 1140. FIG. 11B illustrates a layered PCD precursorassembly 1120 of a first layer 1122 of a mass of diamond particleshaving a fine average particle size (e.g., an average particle size ofabout 10 μm to about 20 μm, less than about 30 μm, about 20 to about 40μm, or about 11 μm to about 19.5 μm, greater than 10 μm, about 10 μm toabout 20 μm, less than about 20 μm, less than about 25 μm, about 15 μmto about 25 μm, or about 20 μm) adjacent to a second layer 1124 of amass of diamond particles having a coarse average particle size that isgreater than the fine average particle size of the first layer 1122(e.g., at least about 40 μm, about 40 μm to about 60 μm, about 30 μm toabout 50 μm, greater than about 20 μm, greater than about 30 μm, about20 μm to about 40 μm, about 20 μm to about 50 μm, about 35 μm to about45 μm, about 40 μm, about 1.5 to about 4 times the fine average particlesize, about 2 to about 2.5 times the fine average particle size, etc.).The second layer 1124 may include about 2% to about 8% by weighttungsten, tungsten carbide, sintered tungsten carbide, or combinationsthereof. Although the illustrated embodiment of the PDC precursorassembly 1120 only utilizes two layers of diamond particles, two ormore, or more than three layers may be employed. In one embodiment, eachlayer may have a progressively smaller average diamond particle sizewith distance away from the substrate 1104.

As shown in FIG. 11B, the layered PCD precursor assembly 1120 ispositioned adjacent to the interfacial surface 1108 of the substrate1104. As previously discussed, the substrate 1104 may include ametal-solvent catalyst. The layered PCD precursor assembly 1120 and thesubstrate 1104 may be subjected to an HPHT process using conditionspreviously described with respect to sintering the PCD embodimentsdisclosed herein. The PDC 1140 so-formed includes the PCD table 1130that comprises PCD that is integrally formed with the substrate 1104 andbonded to the interfacial surface 1108 of the substrate 1104. If thesubstrate 1104 includes a metal-solvent catalyst, the metal-solventcatalyst may liquefy and infiltrate the layered PCD precursor assembly1120 to promote growth between adjacent diamond particles of the layeredPCD precursor assembly 1120 to form the PCD table 1130 comprised of abody of bonded diamond grains having the infiltrated metal-solventcatalyst interstitially disposed between the bonded diamond grains. Forexample, if the substrate 1104 is a cobalt-cemented tungsten carbidesubstrate, cobalt from the substrate 1104 may be liquefied andinfiltrate the layered PCD precursor assembly 1120 to catalyze formationof the PCD table 1140. Providing a coarser layer of diamond particles(e.g., coarse diamond particle of the second layer 1124) adjacent to thesubstrate 1104 may prevent or at least reduce braze cracking when thePDC 1140 is brazed to a structure such as bit body of a rotary drillbit.

The PCD precursor assembly 1120 may be subjected to HPHT processing atany of the HPHT conditions disclosed herein. The PCD table 1130 of thePDC 1140 so-formed may exhibit two distinct diamond grain layers, afirst layer 1132 adjacent to the substrate including coarse-sizeddiamond grains exhibiting a coarse-sized average grain size, and asecond layer 1134 adjacent to the first layer including fine-sizeddiamond grains exhibiting a fine-sized average grain size smaller thanthe coarse-sized average grain size. The average diamond grain sizes maybe the same or similar to that of average diamond particle sizes used toform it. For example, an average diamond grain size of the first layer1132 may be the same or similar to that of the coarse diamond particlesize of the second layer 1124 and the average diamond grain size of thesecond layer 1134 may be the same or similar to that of the fine averagediamond particle size of the first layer 1122. As another example, theaverage diamond grain size of the first layer 1132 may have a coarseaverage diamond grain size of greater than about 20 μm, greater thanabout 30 μm, about 20 μm to about 40 μm, about 30 μm to about 40 μm,about 20 μm to about 50 μm, about 40 μm to about 50 μm, or about 35 μmto about 45 μm. The average diamond grain size of the second layer 1134may have a fine average diamond grain size of greater than about 10 μm,about 10 μm to about 20 μm, less than about 20 μm, less than about 25μm, about 15 μm to about 25 μm, and about 15 μm to about 20 μm.

In another embodiment, a PCD table may be fabricated according to any ofthe disclosed embodiments in a first HPHT process, leached to removesubstantially all of the metal-solvent catalyst from the interstitialregions between the bonded diamond grains, and subsequently bonded to asubstrate in a second HPHT process. In the second HPHT process, aninfiltrant from, for example, a cemented carbide substrate mayinfiltrate into the interstitial regions from which the metal-solventcatalyst was depleted. For example, the infiltrant may be cobalt that isswept-in from a cobalt-cemented tungsten carbide substrate. In oneembodiment, the first and/or second HPHT process may be performed at apressure of at least about 7.5 GPa. In one embodiment, the infiltrantmay be leached from the infiltrated PCD table using a second acidleaching process following the second HPHT process.

In some embodiments, the pressure employed in the HPHT process used tofabricate the PDC 300 may be sufficient to reduce residual stresses inthe PCD table 302 that develop during the HPHT process due to thethermal expansion mismatch between the substrate 304 and the PCD table302. In such an embodiment, the principal stress measured on the workingsurface 303 of the PDC 300 may exhibit a value of about −345 MPa toabout 0 MPa, such as about −289 MPa. For example, the principal stressmeasured on the working surface 303 may exhibit a value of about −345MPa to about 0 MPa. A conventional PDC fabricated using an HPHT processat a pressure below about 7.5 GPa may result in a PCD table thereofexhibiting a principal stress on a working surface thereof of about−1724 MPa to about −414 MPa, such as about −770 MPa.

Residual stress may be measured on the working surface 303 of the PCDtable 302 of the PDC 300 as described in T. P. Lin, M. Hood, G. A.Cooper, and R. H. Smith, “Residual stresses in polycrystalline diamondcompacts,” J. Am. Ceram. Soc. 77, 6, 1562-1568 (1994). Moreparticularly, residual strain may be measured with a rosette strain gagebonded to the working surface 303. Such strain may be measured fordifferent levels of removal of the substrate 304 (e.g., as material isremoved from the back of the substrate 304). Residual stress may becalculated from the measured residual strain data.

FIG. 12 is a graph of residual principal stress versus substratethickness that was measured in a PCD table of a PDC fabricated atpressure above about 7.5 GPa in accordance with an embodiment of theinvention and a PCD table of a conventionally formed PDC. The residualprincipal stress was determined using the technique described in thearticle referenced above by Lin et al. Curve 1210 shows the measuredresidual principal stress on a working surface of the PDC fabricated ata pressure above about 7.5 GPa. The PDC that was fabricated at apressure above about 7.5 GPa had a thickness dimension of about 1 mm andthe substrate had a thickness dimension of about 7 mm and a diameter ofabout 13 mm. Curve 1212 shows the measured residual principal stress ona working surface of a PCD table of a conventionally PDC fabricated atpressure below about 7.5 GPa. The PDC that was fabricated at a pressurebelow about 7.5 GPa had a thickness dimension of about 1 mm and thesubstrate had a thickness dimension of about 7 mm and a diameter ofabout 13 mm. The highest absolute value of the residual principal stressoccurs with the full substrate length of about 7 mm. As shown by thecurves 1210 and 1212, increasing the pressure, employed in the HPHTprocess used to fabricate a PDC, above about 7.5 GPa may reduce thehighest absolute value of the principal residual stress in a PCD tablethereof by about 60% relative to a conventionally fabricated PDC. Forexample, at the full substrate length, the absolute value of theprincipal residual stress in the PCD table fabricated at a pressureabove about 7.5 GPa is about 60% less than the absolute value of theprincipal residual stress in the PCD table of the conventionallyfabricated PDC.

The following working examples provide further detail about the magneticproperties of PCD tables of PDCs fabricated in accordance with theprinciples of some of the specific embodiments of the invention. Themagnetic properties of each PCD table listed in Tables I-IV were testedusing a KOERZIMAT CS 1.096 instrument that is commercially availablefrom Foerster Instruments of Pittsburgh, Pa. The specific magneticsaturation of each PCD table was measured in accordance with ASTMB886-03 (2008) and the coercivity of each PCD table was measured usingASTM B887-03 (2008)e1 using a KOERZIMAT CS 1.096 instrument. The amountof cobalt-based metal-solvent catalyst in the tested PCD tables wasdetermined using energy dispersive spectroscopy and Rutherfordbackscattering spectroscopy. The specific magnetic saturation constantof the cobalt-based metal-solvent catalyst in the tested PCD tables wasdetermined to be about 201 G·cm³/g using an iterative analysis aspreviously described. When a value of 201 G·cm³/g was used for thespecific magnetic saturation constant of the cobalt-based metal-solventcatalyst, the calculated amount of the cobalt-based metal-solventcatalyst in the tested PCD tables using the analysis software of theKOERZIMAT CS 1.096 instrument substantially matched the measurementsusing energy dispersive spectroscopy and Rutherford spectroscopy.

Table I below lists PCD tables that were fabricated in accordance withthe principles of certain embodiments of the invention discussed above.Each PCD table was fabricated by placing a mass of diamond particleshaving the listed average diamond particle size adjacent to acobalt-cemented tungsten carbide substrate in a niobium container,placing the container in a high-pressure cell medium, and subjecting thehigh-pressure cell medium and the container therein to an HPHT processusing an HPHT cubic press to form a PCD table bonded to the substrate.The surface area of each anvil of the HPHT press and the hydraulic linepressure used to drive the anvils were selected so that the sinteringpressure was at least about 7.8 GPa. The temperature of the HPHT processwas about 1400° C. and the sintering pressure was at least about 7.8GPa. The sintering pressures listed in Table I refer to the pressure inthe high-pressure cell medium at room temperature, and the actualsintering pressures at the sintering temperature are believed to begreater. After the HPHT process, the PCD table was removed from thesubstrate by grinding away the substrate. However, the substrate mayalso be removed using electro-discharge machining or another suitablemethod.

TABLE I Selected Magnetic Properties of PCD Tables Fabricated Accordingto Embodiments of the Invention Specific Average Sintering MagneticSpecific Diamond Pressure Saturation Calculated Coercivity PermeabilityParticle Size (μm) (GPa) (G · cm³/g) Co wt % (Oe) (G · cm³/g · Oe) 1 207.8 11.15 5.549 130.2 0.08564 2 19 7.8 11.64 5.792 170.0 0.06847 3 197.8 11.85 5.899 157.9 0.07505 4 19 7.8 11.15 5.550 170.9 0.06524 5 197.8 11.43 5.689 163.6 0.06987 6 19 7.8 10.67 5.150 146.9 0.07263 7 197.8 10.76 5.357 152.3 0.07065 8 19 7.8 10.22 5.087 145.2 0.07039 9 197.8 10.12 5.041 156.6 0.06462 10 19 7.8 10.72 5.549 137.1 0.07819 11 117.8 12.52 6.229 135.3 0.09254 12 11 7.8 12.78 6.362 130.5 0.09793 13 117.8 12.69 6.315 134.6 0.09428 14 11 7.8 13.20 6.569 131.6 0.1003

Table II below lists conventional PCD tables that were fabricated. EachPCD table listed in Table II was fabricated by placing a mass of diamondparticles having the listed average diamond particle size adjacent to acobalt-cemented tungsten carbide substrate in a niobium container,placing the container in a high-pressure cell medium, and subjecting thehigh-pressure cell medium and the container therein to an HPHT processusing an HPHT cubic press to form a PCD table bonded to the substrate.The surface area of each anvil of the HPHT press and the hydraulic linepressure used to drive the anvils were selected so that the sinteringpressure was about 4.6 GPa. Except for samples 15, 16, 18, and 19, whichwere subjected to a temperature of about 1430° C., the temperature ofthe HPHT process was about 1400° C. and the sintering pressure was about4.6 GPa. The sintering pressures listed in Table II refer to thepressure in the high-pressure cell medium at room temperature. After theHPHT process, the PCD table was removed from the cobalt-cementedtungsten carbide substrate by grinding away the cobalt-cemented tungstencarbide substrate.

TABLE II Selected Magnetic Properties of Several Conventional PCD TablesSpecific Average Sintering Magnetic Specific Diamond Pressure SaturationCalculated Coercivity Permeability Particle Size (μm) (GPa) (G · cm³/g)Co wt % (Oe) (G · cm³/g · Oe) 15 20 4.61 19.30 9.605 94.64 0.2039 16 204.61 19.52 9.712 96.75 0.2018 17 20 4.61 19.87 9.889 94.60 0.2100 18 205.08 18.61 9.260 94.94 0.1960 19 20 5.08 18.21 9.061 100.4 0.1814 20 205.86 16.97 8.452 108.3 0.1567 21 20 4.61 17.17 8.543 102.0 0.1683 22 204.61 17.57 8.745 104.9 0.1675 23 20 5.08 16.10 8.014 111.2 0.1448 24 205.08 16.79 8.357 107.1 0.1568

As shown in Tables I and II, the conventional PCD tables listed in TableII exhibit a higher cobalt content therein than the PCD tables listed inTable I as indicated by the relatively higher specific magneticsaturation values. Additionally, the conventional PCD tables listed inTable II exhibit a lower coercivity indicative of a relatively greatermean free path between diamond grains, and thus may indicate relativelyless diamond-to-diamond bonding between the diamond grains. Thus, thePCD tables according to examples of the invention listed in Table I mayexhibit significantly less cobalt therein and a lower mean free pathbetween diamond grains than the PCD tables listed in Table II.

Table III below lists conventional PCD tables that were obtained fromPDCs. Each PCD table listed in Table III was separated from acobalt-cemented tungsten carbide substrate bonded thereto by grinding.

TABLE III Selected Magnetic Properties of Several Conventional PCDTables Specific Magnetic Specific Saturation Calculated CoercivityPermeability (G · cm³/g) Co wt % (Oe) (G · cm³/g · Oe) 25 17.23 8.572140.4 0.1227 26 16.06 7.991 150.2 0.1069 27 15.19 7.560 146.1 0.1040 2817.30 8.610 143.2 0.1208 29 17.13 8.523 152.1 0.1126 30 17.00 8.458142.5 0.1193 31 17.08 8.498 147.2 0.1160 32 16.10 8.011 144.1 0.1117

Table IV below lists conventional PCD tables that were obtained fromPDCs. Each PCD table listed in Table IV was separated from acobalt-cemented tungsten carbide substrate bonded thereto by grindingthe substrate away. Each PCD table listed in Table IV and tested had aleached region from which cobalt was depleted and an unleached region inwhich cobalt is interstitially disposed between bonded diamond grains.The leached region was not removed. However, to determine the specificmagnetic saturation and the coercivity of the unleached region of thePCD table having metal-solvent catalyst occupying interstitial regionstherein, the leached region may be ground away so that only theunleached region of the PCD table remains. It is expected that theleached region causes the specific magnetic saturation to be lower andthe coercivity to be higher than if the leached region was removed andthe unleached region was tested.

TABLE IV Selected Magnetic Properties of Several Conventional LeachedPCD Tables Specific Magnetic Specific Saturation Calculated CoercivityPermeability (G · cm³/g) Co wt % (Oe) (G · cm³/g · Oe) 33 17.12 8.471143.8 0.1191 34 13.62 6.777 137.3 0.09920 35 15.87 7.897 140.1 0.1133 3612.95 6.443 145.5 0.0890 37 13.89 6.914 142.0 0.09782 38 13.96 6.946146.9 0.09503 39 13.67 6.863 133.8 0.1022 40 12.80 6.369 146.3 0.08749

As shown in Tables I, III, and IV, the conventional PCD tables of TablesIII and IV exhibit a higher cobalt content therein than the PCD tableslisted in Table I as indicated by the relatively higher specificmagnetic saturation values. This is believed by the inventors to be aresult of the PCD tables listed in Tables III and IV being formed bysintering diamond particles having a relatively greater percentage offine diamond particles than the diamond particle formulations used tofabricate the PCD tables listed in Table I.

A similar correlation between higher cobalt content and increasedelectrical conductivity properties of PCD tables has also been observed.Sensitivity of electrical conductivity measurements of PDC diamondtables of a given PCD microstructure may provide an excellent method forestimation and imaging of metal content in the diamond table. Such typesof estimates are sensitive to changes in bulk average metal-solventcontent and local changes in the metal-solvent content, allowing for asensitive estimation of both metal content and cutting performance.

Referring back to FIGS. 9 and 10, electrical conductivity trends withmetal-solvent content suggest that lowering the metal-solvent content,and thus the electrical conductivity, increases performance of a PDC. Infact, relatively lowered metal-solvent content in the PDC appears tosubstantially influence cutting performance. Therefore, it follows thatthe electrical conductivity, also dependent on metal-solvent catalystcontent, may also be used as a quality characteristic for evaluating PDCcutting performance. For example, a PCD cutting element with electricalconductivities below about 1200 S/m (in an unleached region of PCD) havebeen found to increase cutting performance.

Embodiments of Applications for PCD and PDCs

The disclosed PCD and PDC embodiments may be used in a number ofdifferent applications including, but not limited to, use in a rotarydrill bit (FIGS. 13 and 14), a thrust-bearing apparatus (FIG. 15), aradial bearing apparatus (FIG. 16), a subterranean drilling system (FIG.17), and a wire-drawing die (FIG. 18). The various applicationsdiscussed above are merely some examples of applications in which thePCD and PDC embodiments may be used. Other applications arecontemplated, such as employing the disclosed PCD and PDC embodiments infriction stir welding tools.

FIG. 13 is an isometric view and FIG. 14 is a top elevation view of anembodiment of a rotary drill bit 800. The rotary drill bit 800 includesat least one PDC configured according to any of the previously describedPDC embodiments. The rotary drill bit 800 comprises a bit body 802 thatincludes radially and longitudinally extending blades 804 with leadingfaces 806, and a threaded pin connection 808 for connecting the bit body802 to a drilling string. The bit body 802 defines a leading endstructure for drilling into a subterranean formation by rotation about alongitudinal axis 810 and application of weight-on-bit. At least one PDCcutting element, configured according to any of the previously describedPDC embodiments (e.g., the PDC 300 shown in FIG. 3A), may be affixed tothe bit body 802. With reference to FIG. 14, a plurality of PDCs 812 aresecured to the blades 804. For example, each PDC 812 may include a PCDtable 814 bonded to a substrate 816. More generally, the PDCs 812 maycomprise any PDC disclosed herein, without limitation. In addition, ifdesired, in some embodiments, a number of the PDCs 812 may beconventional in construction. Also, circumferentially adjacent blades804 define so-called junk slots 818 therebetween, as known in the art.Additionally, the rotary drill bit 800 may include a plurality of nozzlecavities 820 for communicating drilling fluid from the interior of therotary drill bit 800 to the PDCs 812.

FIGS. 13 and 14 merely depict an embodiment of a rotary drill bit thatemploys at least one cutting element comprising a PDC fabricated andstructured in accordance with the disclosed embodiments, withoutlimitation. The rotary drill bit 800 is used to represent any number ofearth-boring tools or drilling tools, including, for example, core bits,roller-cone bits, fixed-cutter bits, eccentric bits, bicenter bits,reamers, reamer wings, or any other downhole tool including PDCs,without limitation.

The PCD and/or PDCs disclosed herein (e.g., the PDC 300 shown in FIG.3A) may also be utilized in applications other than rotary drill bits.For example, the disclosed PDC embodiments may be used in thrust-bearingassemblies, radial bearing assemblies, wire-drawing dies, artificialjoints, machining elements, and heat sinks.

FIG. 15 is an isometric cut-away view of an embodiment of athrust-bearing apparatus 900, which may utilize any of the disclosed PDCembodiments as bearing elements. The thrust-bearing apparatus 900includes respective thrust-bearing assemblies 902. Each thrust-bearingassembly 902 includes an annular support ring 904 that may be fabricatedfrom a material, such as carbon steel, stainless steel, or anothersuitable material. Each support ring 904 includes a plurality ofrecesses (not labeled) that receive a corresponding bearing element 906.Each bearing element 906 may be mounted to a corresponding support ring904 within a corresponding recess by brazing, press-fitting, usingfasteners, or another suitable mounting technique. One or more, or allof bearing elements 906 may be configured according to any of thedisclosed PDC embodiments. For example, each bearing element 906 mayinclude a substrate 908 and a PCD table 910, with the PCD table 910including a bearing surface 912.

In use, the bearing surfaces 912 of one of the thrust-bearing assemblies902 bear against the opposing bearing surfaces 912 of the other one ofthe bearing assemblies 902. For example, one of the thrust-bearingassemblies 902 may be operably coupled to a shaft to rotate therewithand may be termed a “rotor.” The other one of the thrust-bearingassemblies 902 may be held stationary and may be termed a “stator.”

FIG. 16 is an isometric cut-away view of an embodiment of a radialbearing apparatus 1000, which may utilize any of the disclosed PDCembodiments as bearing elements. The radial bearing apparatus 1000includes an inner race 1002 positioned generally within an outer race1004. The outer race 1004 includes a plurality of bearing elements 1006affixed thereto that have respective bearing surfaces 1008. The innerrace 1002 also includes a plurality of bearing elements 1010 affixedthereto that have respective bearing surfaces 1012. One or more, or allof the bearing elements 1006 and 1010 may be configured according to anyof the PDC embodiments disclosed herein. The inner race 1002 ispositioned generally within the outer race 1004, and thus the inner race1002 and outer race 1004 may be configured so that the bearing surfaces1008 and 1012 may at least partially contact one another and moverelative to each other as the inner race 1002 and outer race 1004 rotaterelative to each other during use.

The radial bearing apparatus 1000 may be employed in a variety ofmechanical applications. For example, so-called “roller-cone” rotarydrill bits may benefit from a radial-bearing apparatus disclosed herein.More specifically, the inner race 1002 may be mounted to a spindle of aroller cone and the outer race 1004 may be mounted to an inner boreformed within a cone and such an outer race 1004 and inner race 1002 maybe assembled to form a radial bearing apparatus.

Referring to FIG. 17, the thrust-bearing apparatus 900 and/or radialbearing apparatus 1000 may be incorporated in a subterranean drillingsystem. FIG. 17 is a schematic isometric cut-away view of a subterraneandrilling system 1100 that includes at least one of the thrust-bearingapparatuses 900 shown in FIG. 15 according to another embodiment. Thesubterranean drilling system 1100 includes a housing 1102 enclosing adownhole drilling motor 1104 (i.e., a motor, turbine, or any otherdevice capable of rotating an output shaft) that is operably connectedto an output shaft 1106. A first thrust-bearing apparatus 900 ₁ (FIG.15) is operably coupled to the downhole drilling motor 1104. A secondthrust-bearing apparatus 900 ₂ (FIG. 15) is operably coupled to theoutput shaft 1106. A rotary drill bit 1108 configured to engage asubterranean formation and drill a borehole is connected to the outputshaft 1106. The rotary drill bit 1108 is shown as a roller-cone bitincluding a plurality of roller cones 1110. However, other embodimentsmay utilize different types of rotary drill bits, such as a so-called“fixed-cutter” drill bit shown in FIGS. 13 and 14. As the borehole isdrilled, pipe sections may be connected to the subterranean drillingsystem 1100 to form a drill string capable of progressively drilling theborehole to a greater depth within the earth.

A first one of the thrust-bearing assemblies 902 of the thrust-bearingapparatus 900 ₁ is configured as a stator that does not rotate and asecond one of the thrust-bearing assemblies 902 of the thrust-bearingapparatus 900 ₁ is configured as a rotor that is attached to the outputshaft 1106 and rotates with the output shaft 1106. The on-bottom thrustgenerated when the drill bit 1108 engages the bottom of the borehole maybe carried, at least in part, by the first thrust-bearing apparatus 900₁. A first one of the thrust-bearing assemblies 902 of thethrust-bearing apparatus 900 ₂ is configured as a stator that does notrotate and a second one of the thrust-bearing assemblies 902 of thethrust-bearing apparatus 900 ₂ is configured as a rotor that is attachedto the output shaft 1106 and rotates with the output shaft 1106. Fluidflow through the power section of the downhole drilling motor 1104 maycause what is commonly referred to as “off-bottom thrust,” which may becarried, at least in part, by the second thrust-bearing apparatus 900 ₂.

In operation, drilling fluid may be circulated through the downholedrilling motor 1104 to generate torque and effect rotation of the outputshaft 1106 and the rotary drill bit 1108 attached thereto so that aborehole may be drilled. A portion of the drilling fluid may also beused to lubricate opposing bearing surfaces of the bearing elements 906of the thrust-bearing assemblies 902.

FIG. 18 is a side cross-sectional view of an embodiment of awire-drawing die 1200 that employs a PDC 1202 fabricated in accordancewith the teachings described herein. The PDC 1202 includes an inner,annular PCD region 1204 comprising any of the PCD tables describedherein that is bonded to an outer cylindrical substrate 1206 that may bemade from the same materials as the substrate 304 shown in FIG. 3A. ThePCD region 1204 also includes a die cavity 1208 formed therethroughconfigured for receiving and shaping a wire being drawn. Thewire-drawing die 1200 may be encased in a housing (e.g., a stainlesssteel housing), which is not shown, to allow for handling.

In use, a wire 1210 of a diameter “d₁” is drawn through die cavity 1208along a wire-drawing axis 1212 to reduce the diameter of the wire 1210to a reduced diameter “d₂.”

While various aspects and embodiments have been disclosed herein, otheraspects and embodiments are contemplated. The various aspects andembodiments disclosed herein are for purposes of illustration and arenot intended to be limiting. Additionally, the words “including,”“having,” and variants thereof (e.g., “includes” and “has”) as usedherein, including the claims, shall be open ended and have the samemeaning as the word “comprising” and variants thereof (e.g., “comprise”and “comprises”).

The invention claimed is:
 1. A polycrystalline diamond compact,comprising: a polycrystalline diamond table, at least an unleachedportion of the polycrystalline diamond table including: a plurality ofdiamond grains directly bonded together via diamond-to-diamond bondingto define interstitial regions, the plurality of diamond grainsexhibiting an average grain size of about 50 μm or less; a catalystoccupying at least a portion of the interstitial regions; wherein theunleached portion of the polycrystalline diamond table exhibits acoercivity of about 115 Oe or more; wherein the unleached portion of thepolycrystalline diamond table exhibits an average electricalconductivity of less than about 1200 S/m; and wherein the unleachedportion of the polycrystalline diamond table exhibits a G_(ratio) of atleast about 4.0×10⁶; and a substrate bonded to the polycrystallinediamond table.
 2. The polycrystalline diamond compact of claim 1 whereinthe coercivity is about 115 Oe to about 250 Oe.
 3. The polycrystallinediamond compact of claim 2 wherein the coercivity is about 130 Oe toabout 160 Oe.
 4. The polycrystalline diamond compact of claim 1 whereinthe unleached portion of the polycrystalline diamond table exhibits aspecific magnetic saturation of about 15 G·cm³/g or less.
 5. Thepolycrystalline diamond compact of claim 4 wherein: the coercivity isabout 115 Oe to about 175 Oe; the specific magnetic saturation is about10 G·cm³/g to about 15 G·cm³/g; and the unleached portion of thepolycrystalline diamond table includes metal-solvent catalyst in anamount of about 3 weight % to about 7.5 weight %.
 6. The polycrystallinediamond compact of claim 1 wherein the average electrical conductivityis about 25 S/m to about 1000 S/m.
 7. The polycrystalline diamondcompact of claim 6 wherein the average electrical conductivity is about100 S/m to about 500 S/m.
 8. The polycrystalline diamond compact ofclaim 1 wherein the coercivity is about 115 Oe to about 175 Oe.
 9. Thepolycrystalline diamond compact of claim 8 wherein the averageelectrical conductivity is less than 750 S/m.
 10. The polycrystallinediamond compact of claim 8 wherein the unleached portion of thepolycrystalline diamond table exhibits a specific magnetic saturation ofabout 5 G·cm³/g to about 15 G·cm³/g.
 11. The polycrystalline diamondcompact of claim 5 wherein the G_(ratio) is about 5.0×10⁶ to about15×10⁶.
 12. The polycrystalline diamond compact of claim 5 wherein theunleached portion of the polycrystalline diamond table exhibits aspecific permeability less than about 0.10 G·cm³/(g·Oe).
 13. Thepolycrystalline diamond compact of claim 1 wherein the catalyst ispresent in the unleached portion of the polycrystalline diamond table inan amount greater than 0 weight % to about 7.5 weight %.
 14. Thepolycrystalline diamond compact of claim 1 wherein the average grainsize is about 30 μm or less.
 15. The polycrystalline diamond compact ofclaim 1 wherein: the polycrystalline diamond table includes an upperworking surface and an interfacial surface bonded to the substrate; andthe average electrical conductivity of the polycrystalline diamond tabledecreases with distance from the upper working surface toward thesubstrate.
 16. The polycrystalline diamond compact of claim 1 whereinthe polycrystalline diamond table is formed from only single layer ofpolycrystalline diamond extending from an upper working surface of thepolycrystalline diamond table to the substrate.
 17. The polycrystallinediamond compact of claim 1 wherein the polycrystalline diamond tableincludes: a first layer including coarse-sized diamond grains exhibitinga first average grain size; and a second layer including fine-sizeddiamond grains exhibiting a second average grain size less than thefirst average grain size, the first layer disposed between the secondlayer and the substrate.
 18. A polycrystalline diamond compact,comprising: a polycrystalline diamond table, at least an unleachedportion of the polycrystalline diamond table including: a plurality ofdiamond grains directly bonded together via diamond-to-diamond bondingto define interstitial regions, the plurality of diamond grainsexhibiting an average grain size of about 30 μm or less; a catalystoccupying at least a portion of the interstitial regions; wherein theunleached portion of the polycrystalline diamond table exhibits acoercivity of about 115 Oe to about 175 Oe; wherein the unleachedportion of the polycrystalline diamond table exhibits an averageelectrical conductivity of less than about 1200 S/m; and wherein theunleached portion of the polycrystalline diamond table exhibits athermal stability, as determined by distance cut, prior to failure in avertical lathe test, of at least about 1300 m.
 19. A polycrystallinediamond compact, comprising: a polycrystalline diamond table, at leastan unleached portion of the polycrystalline diamond table including: aplurality of diamond grains directly bonded together viadiamond-to-diamond bonding to define interstitial regions, the pluralityof diamond grains exhibiting an average grain size of about 50 μm orless; a catalyst occupying at least a portion of the interstitialregions, the catalyst is present in the unleached portion of thepolycrystalline diamond table in an amount greater than about 0 weight %to about 7.5 weight %; wherein the unleached portion of thepolycrystalline diamond table exhibits a coercivity of about 115 Oe ormore; wherein the unleached portion of the polycrystalline diamond tableexhibits an average electrical conductivity of less than about 1200 S/m;and wherein the unleached portion of the polycrystalline diamond tableexhibits a thermal stability, as determined by distance cut, prior tofailure, in a vertical lathe test, of about 1300 m; and a substratebonded to the polycrystalline diamond table.
 20. The polycrystallinediamond compact of claim 18 wherein the polycrystalline diamond tableincludes a leached region, and wherein the unleached portion of thepolycrystalline diamond table is disposed between the substrate and theleached region.
 21. The polycrystalline diamond compact of claim 20wherein the coercivity of the unleached portion of the polycrystallinediamond table is about 130 Oe to about 160 Oe.
 22. The polycrystallinediamond compact of claim 18 wherein the coercivity of the unleachedportion of the polycrystalline diamond table is about 155 Oe to about175 Oe.
 23. The polycrystalline diamond compact of claim 22 wherein theplurality of diamond grains and the metal-solvent catalyst of theunleached portion of the polycrystalline diamond table collectivelyexhibit a specific permeability of about 0.060 to about 0.090G·cm³/g·Oe.
 24. The polycrystalline diamond compact of claim 23 whereinthe polycrystalline diamond table exhibits a G_(ratio) of at least about30.0×10⁶.
 25. The polycrystalline diamond compact of claim 23 whereinthe unleached portion of the polycrystalline diamond table exhibits aG_(ratio) of at least about 5.0×10⁶ to about 15.0×10⁶.
 26. Thepolycrystalline diamond compact of claim 19 wherein the polycrystallinediamond table includes a leached region, and wherein the portion of thepolycrystalline diamond table is disposed between the substrate and theleached region.
 27. The polycrystalline diamond compact of claim 26wherein the coercivity of the unleached portion of the polycrystallinediamond table is about 130 Oe to about 160 Oe.
 28. The polycrystallinediamond compact of claim 19 wherein the coercivity of the unleachedportion of the polycrystalline diamond table is about 155 Oe to about175 Oe.
 29. The polycrystalline diamond compact of claim 28 wherein theplurality of diamond grains and the metal-solvent catalyst of theunleached portion of the polycrystalline diamond table collectivelyexhibit a specific permeability of about 0.060 to about 0.090G·cm³/g·Oe.
 30. The polycrystalline diamond compact of claim 29 whereinthe polycrystalline diamond table exhibits a G_(ratio) of at least about30.0×10⁶.
 31. A rotary drill bit, comprising: a bit body including aleading end structure configured to facilitate drilling a subterraneanformation; and a plurality of cutting elements mounted to the bit body,at least one of the plurality of cutting elements configured as thepolycrystalline diamond compact according to claim
 1. 32. A rotary drillbit, comprising: a bit body including a leading end structure configuredto facilitate drilling a subterranean formation; and a plurality ofcutting elements mounted to the bit body, at least one of the pluralityof cutting elements configured as the polycrystalline diamond compactaccording to claim
 18. 33. A rotary drill bit, comprising: a bit bodyincluding a leading end structure configured to facilitate drilling asubterranean formation; and a plurality of cutting elements mounted tothe bit body, at least one of the plurality of cutting elementsconfigured as the polycrystalline diamond compact according to claim 19.